JPH0327306B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method for producing a large number of weld beads with independent circumferential shapes separated from each other, and is particularly applicable to the continuous welding of a series of tubes onto a tube sheet. be done.

For welding tubes onto a tube sheet, in particular for producing heat exchangers consisting of a number of tubes, the ends of which are inserted into holes drilled in the tube sheet, a torch and said torch are used. Automatic welding heads are commonly used which include a moving device, the latter device making it possible to move the torch along different directions and track the circumference to be welded one by one.

Although there are a wide variety of welding systems, in most cases the degree of automation of the welding process is limited to single circumference welding. Therefore, the operator moves the welding head over the pipe to be welded, places the torch at the starting point of the first weld bead, then ignites the arc and automatically moves the torch along the circumference to be welded. Welding had to be carried out. At the end of the weld, it is customary to pass through the starting point to complete the weld. The operator then stops the torch, cuts the arc, and then aligns the welding head with the next tube. In this manner, the operator intervenes after each bead is welded to align the welding head with the next tube and set the torch at the starting point of the new bead to be welded. Such operations are delicate and time consuming. On the other hand, the arc must be ignited for each weld bead and cut off at the end of the weld bead. Such transient steps are difficult to control and are prone to local failures, red flames due to ignition flash, or micro-porosity during arc activation.

A continuous welding method is also known in which all the tubes are plugged, in which the entire tube is welded to the plate and the tube is then made. The above welding method significantly increases the length of the weld bead and requires machining after welding.

The object of the present invention is to provide a new welding method that can eliminate the above-mentioned drawbacks by performing welding continuously and automatically.

According to the invention, the arc is ignited in a conventional manner, and the torch is placed on the first circumference to be welded, and then after making the first weld bead, the torch is turned off in order to partially extinguish the arc. The intensity is reduced to keep the arc itself lit without melting the parts, and then the second part to be welded.
moving the torch to a starting position on the circumference, at said position returning the arc strength to a welding strength to perform static pre-melting, and creating a second weld bead along the second circumference to be welded; then reducing the torch intensity and again performing a partial extinguishment of the arc and moving the torch again to the starting point on the third circumference to be welded;
At this point, the arc is brought back to welding strength for static premelting, and then a third weld bead is created, thus moving from one round to the next, and the adjustment of welding factors is automatic until the last weld bead. The arc is cut after the final weld bead is completed.

In a special embodiment where the weld bead has a closed circumferential shape, the torch is aligned at the starting point of the weld bead and, after static premelting, the weld bead is created along the circumference and completely melted. After passing the starting point to perform the weld, the arc intensity is reduced to partially extinguish the arc, and then the torch is directed along the circumference above the already made weld bead to the next weld bead. The arc remains partially extinguished until the point of displacement.

To weld multiple tubes onto a tubesheet and arrange the ends of the tubes in multiple parallel rows, align the torch on the axis of one side of the first row and ignite the arc. ,
The torch is moved along the axis to point _A1 on the circumference of the first pipe to be welded, static preliminary melting is performed for a limited time at point A1, and then the torch is moved around the entire circumference to A1. A weld bead is created past the point B1, and the arc is partially extinguished by reducing the arc intensity at the point B1.Then, the torch with the arc partially extinguished is circled to a point C1 on the opposite side of A1. Then, move it along the axis to point A2 on the circumference of the second pipe in the row, weld to point B2 in the same manner as above, and then partially extinguish the arc. move the torch to point C2 on the axis of the row, then move it along the axis to the third tube, and thus repeat the above until the last tube Tn of the first row, where the section Move the torch of the extinguished arc along the weld bead made up to Cn, move the torch from the above point Cn to the axis of the second row, and then move it to the end of the second row. a point on a pipe
Move the torch along the above axis to A'1,
The second row of tubes is welded in the same manner as described above, moving on to the next row in this manner. Preferably,
The automatic movement of the torch and the adjustment of welding factors are performed by numerical control equipment or a microprocessor.

The present invention will now be described in detail with reference to the accompanying drawings, which are merely examples of welding a number of tubes to a tube sheet.

FIG. 1 schematically shows a part of a tube sheet and the end of a tube to be welded with a welding head 2 with a torch 3. In FIG.

The welding head 2 can be moved continuously on the support 4 along at least three directions x, y and z. On the other hand, the welding head 2 is connected to a welding device 5, which supplies the torch with welding current, protective gas and cooling fluid. The welding device 5 ensures the functions of arc ignition and cutting, and can also adjust the welding factors, especially the arc strength, overall.

Preferably the welding equipment is used for tubesheet welding
It will be TIG type. The reason for this is that the melted part is well-positioned and stable.

The positioning device 4 of the welding head 2 is numerically controlled by a control device 6.
The control device controls the movement of the torch by driving and controlling at least two shafts that create a planar trajectory. A third shaft can also be added to continuously control the intensity of the welding current.

Furthermore, the control device 6 also guides the welding device 5 through a numerical program.

Welding of the tube according to the invention is carried out in the manner shown diagrammatically in FIG. The operator positions the torch 3 at point O on the axis of the row near the first tube of the first row on the tube plate side. The welding head is then moved until the torch is above the point A1 on the circumference of the tube T1 to be welded. As long as the arc is already far from point O, it is fired at point A1, and this A1
A static premelting timed to the welding current takes place at the point.

Thereafter, the process moves to a numerical welding step along the circumference of the tube T1 to be welded, and returning to point A1, lap welding is performed from point A1 to B1 according to the usual method. Here, the welding device 5 guided by the numerical control device 6
Partially extinguish the arc. Therefore, when moving the torch to a point C1 diametrically opposite to point A1, said movement can be carried out without damaging the weld bead that has already been made. Since the arc remains extinguished,
The torch moves along the axis of the tube row until point A2 on tube T2. Traces of this movement remain on the tubesheet, but this is not a disadvantage since the arc is partially extinguished.

The welding device 5 guided by the fixed control device again performs static pre-melting according to the welding current at this point A2, and then the torch moves around the circumference of the pipe T2,
A second weld bead is made up to point B2, which is slightly distant from point B2. As before, the welding current is reduced at this point, but the arc is partially extinguished, and the torch moves beyond the weld bead created to C2, and from this point along the axis of tube T3. Move to A3 above.
In this way, the first row of tubes is expanded one by one until the last tube Tn.
Weld each book one by one. As mentioned above, the arc is extinguished by Bn, so it passes through the weld bead made up to point Cn, moves from Cn with the arc extinguished, and moves to the axis of the second row. It then comes to A'1 on the first tube T1 of the second row along the axis.
Perform a timed static melt and then
Make a weld bead up to B'1. So I extinguished the arc,
Go all the way to C'1, then move on to A'2 on the next tube.
In this way, pass through all the tubes in the second row one by one.
Then move to the third column as before.

Since all tube rows are welded continuously as described above, the arc is completely extinguished after welding the last tube of the last row. If the welding method of the present invention is carried out using conventional automatic welding control equipment, all pipes can be automatically and continuously welded, so that the operator only needs to intervene at the beginning and end of the operation. Since the welding factors are fully controlled by numerical control, it can be used with standard TIG welding equipment. Furthermore, by numerically controlling welding factors and movement trajectories, these can be corrected and weld bead characteristics can be optimized.

Since the various movements are provided by a conventional chain, such as in a machine tool, the disadvantages of miniaturized heads, particularly mechanical clearances and lack of rigidity, can be avoided. In addition, the smoothness of the motor drive and the welding cycle without full cutting of the arc make it possible to produce a very consistent bead. Typically, such welding methods are used only when the torch is perpendicular to the welding surface. However, in the case of welding with electrodes or overlay wires that are inclined to the welding surface, it may be possible to add a motor-driven head between the welder and the torch to provide supplementary motion.

Overall, the invention is not limited to the details of implementation described above. In particular, it is possible to use a large number of welding torches operated by the same chain in order to improve the working tempo,
When welding tubesheets, the welds will be repetitive and uniform. Similarly, in the case of parts with geometric irregularities at the mounting level to be welded, conventional devices for tracing or compensating the trajectory of the torch can also be added to the welding installation. With the above-described device, it is possible to weld along individual circumferences that are not necessarily of the same shape. In particular, when the invention is used for welding tube sheets, if the circumference to be welded cannot be closed separately from each other, and if it is necessary to make a number of weld beads on this circumference, the above-mentioned steps must be taken each time. can be used for other purposes. Although the welding cycle described above is optimal for welding a circular perimeter with many rows, it is possible to modify such a process in which the torch passes continuously over all the perimeters to be welded, Other sequences can also be used. Within the scope of the invention, it is likewise possible to change the positions of the characteristic points, the first ignition point, the static premelting point, the wrap end point and the arc extinction point, the movement start point and the end point, etc.

[Brief explanation of the drawing]

FIG. 1 schematically shows a set of equipment used to carry out the present welding method. FIG. 2 is a diagrammatic top view of the stroke of the torch when welding a series of tubes.

Claims (1)

[Scope of Claims] 1. A method for welding ends of a plurality of tubes aligned in a plurality of parallel rows to a tube sheet by an automatic welding device, the automatic welding device comprising: a welding torch;
automatic control means for displacing said torch along two substantially perpendicular axes in a planar trajectory having for each said tube an annular path following the contour of the tube and a straight path up to the subsequent tube; (a) with said torch on the side of said first row of said parallel rows;
(b) igniting an arc; (c) moving said torch along said axis to a _point A located on the contour of the first tube to be welded; (d) perform a temporary static pre-melting at said point _A ; and (e) create a bead by following said entire contour, passing said point _A and proceeding to point _B. Making,
At this point _B , reduce the applied current slightly to weaken the arc, and (f) trace the torch with the weakened arc along the contour to point _C1 , which is diametrically opposite to point _A. and then along the axis of said first row to point A ₂ located on the contour of the second tube of said row; (g) welding in the same manner up to B ₂ ; h) Place the torch with a weakened arc on the axis of the first row.
C up to ₃ points, and in this way the first
(i _{) displacing said torch with a weakened arc along said bead to C o ;} (j) displacing said torch onto the axis of the second row of said row; (k) welding the second row of tubes and the _following row of tubes; 2. The welding method according to claim 1, wherein automatic displacement of the torch and adjustment of welding parameters are numerically controlled.